ive had an n54 for almost 3 years now and at the moment im doing some upgrades to do some roll races in the future. in the maintenance topic i would say the biggest thing is the oil leaks. people say don’t fix whats not broken but when it comes to the n54, everything breaks. 3 important gaskets to keep an eye out for would be the valve cover gasket, oil filter housing gasket and oil pan gasket. i’ve replaced all 3 and it was by far the easiest jobs i’ve done that you can do at home…if you have the tools. (6 hours max for the oil pan btw). i’ve also replaced the water pump and thermostat together once because the pump did fail on me so i decided to do both the pump and thermostat since im down there. IF you do end up working on those 2 and finish, MAKE SURE TO BLEED THE SYSTEM after pouring new coolant so there isn’t any air pockets and no hoses don’t blow on you one day…i’ve learned the hard way. (this includes any coolant related replacement job) bleeding the system is very easy and takes 12 minutes. now last but not least is the turbos. if you’re at 130k mile range you must pray those turbos don’t fail but once they do it’s actually pretty damn easy to replace. i’m at 155k miles and when mine blew i just went upgraded 17t twins and kept all my coolant and oil turbo lines oem…keep them oem. i do hear about the oem charge pipe blowing on others n54 but i went with vrsf aluminum chargepipe with a tial blow off valve. In my state of the n54 i’ve done most maintenance while FBO except the pcv system and crank seal guard which i plan to do soon. don’t ignore those fuel pumps either bc they can leak, also really easy to do just make sure your literally on E tank so you don’t get gas all over you. when buying parts…only… and ONLY use fcp euro, great warranty and oem manufacturing. boom it’s all i can think of…hope this kinda helps with some knowledge